Electricity: measuring and testing – Electrical speed measuring – Including motor current or voltage sensor
Patent
1993-06-04
1995-06-13
Snow, Walter E.
Electricity: measuring and testing
Electrical speed measuring
Including motor current or voltage sensor
324160, G01P 346, G01P 342
Patent
active
054246369
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process and a device for detecting revolution of a rotating element, and in particular to such a process and device in which the rate of rotation of a rotating part enclosed by a housing is measured.
To determine the rate of rotation of rotating parts, markings which are generally arranged at the rotating part are sensed by an inductive transmitter or an optical sensor. When such marks pass by the stationary transmitter, voltage pulses are generated, the rate of rotation being calculated from the repetition rate of these voltage pulses.
It is not possible to calculate the rate of rotation in this way in the case of rotating parts which are completely enclosed by a housing. For example, in electric fuel pumps which are completely encapsulated, no rotatable parts are guided outward which would make it possible to determine the rate of rotation in a simple manner. For this reason, signals dependent on the rate of rotation have been analyzed in laboratory tests for determining the rate of rotation, e.g.: the oscillation acceleration on the electric fuel pump housing, fluctuations in pressure on the suction side or the pressure side, fluctuations in current in the electric supply lines, fluctuations in the magnetic field outside the electric fuel pumps which are caused by the rotating armature segments with the respective current-carrying alternations.
These signals were determined, for example, by separate sensors and processed in a subsequent evaluating arrangement. Determining the rate of rotation by measuring the intervals between individual oscillations has not proven reliable in the above-mentioned laboratory tests.
ADVANTAGES OF THE INVENTION
The process according to the invention with its characterizing features has the advantage over the prior art that a definite and precise measurement of the rate of rotation is made possible by determining a signal dependent on the rate of rotation and subsequently subjecting it twice to a Fourier transform.
It is particularly advantageous to use the current signal as an additional signal dependent on the rate of rotation in connection with a measurement of the rate of rotation of the electric fuel pump and to subject it to two fast Fourier transforms. The alternating supply of current to the armature windings during the rotation of the armature causes fluctuations in current. These current fluctuations, which occur with an exactly determined frequency which is dependent on the rate of rotation, are detected as maxima in the spectrum after a first Fourier transform; after an additional Fourier transform, the rate of rotation occurs as an absolute maximum and can be evaluated in a simple manner.
A plausibility check is made possible by comparing the rate of rotation determined from the spectrum obtained by a second Fourier transform, e.g. with the main components of the spectrum obtained after the first Fourier transform.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing a device for detecting revolutions of a rotating element in accordance with the present invention;
FIG. 1a shows an internal gear pump schematically;
FIG. 2 shows the measured current curve over time subsequent to bandpass filtering;
FIG. 3 shows the spectrum obtained after the first Fourier transform as a function of the frequency; and
FIG. 4 shows the spectrum obtained after another Fourier transform over time.
DESCRIPTION A PREFERRED EMBODIMENT
FIG. 1 shows an embodiment example of the invention in the form of a block wiring diagram. The electric fuel pump whose rate of rotation is to be determined is designated by 10
Gobernatz Michael
Rollwage Mathias
Thoennissen Jochen
Robert & Bosch GmbH
Snow Walter E.
Striker Michael J.
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